Multi-layer ethylene polymer-based films with polypropylene-based stiffening layer

ABSTRACT

This invention discloses a multi-layer film for making pouches for containing flowable materials, said multi-layer film comprising generally five layers in order: inner sealant-layer, first interposed layer, the core layer, second interposed layer, and the outer sealant layer. The sealant and core layers are ethylene-based, whereas the interposed layers are polypropylene-based. The multi-layer film thickness is in the range of from about 35 microns to about 66 microns. The combined thickness of the first and the second interposed layers is in the range of from about 10% to about 27% of the total thickness of said multi-layer film. Similarly, a combined thickness of the inner and the outer sealant-layers is in the range of from about 10% to about 27% of the total thickness of the multi-layer film. The interposed layers comprise polypropylene that has a melt-index of less than 0.75 dg/min.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/086,557filed Apr. 14, 2011 which is related to U.S. Provisional Application No.61/324,849 filed Apr. 16, 2010, which are incorporated by referenceherein in their entirety.

FIELD OF INVENTION

This invention relates to ethylene polymer based multi-layer films withimproved stiffness and clarity. This invention also relates to a processfor making such multi-layer films, and to pouches for containingflowable materials made from such multi-layer films. More specifically,the present invention relates to films that have polypropylene localizedcloser to the outside surfaces of the multi-layer film so that themulti-layer film not only maintains its mechanical integrity but also isthinner in gauge than currently available films. In one aspect, thepresent invention relates to packaging flowable materials such as milkin pouches using for example, a vertical form, fill, and seal apparatus(“VFFS”) technical field

BACKGROUND

In the VFFS process, a flat web of synthetic thermoplastic film isunwound from a roll and formed into a continuous tube in a tube-formingsection. In the next step, the longitudinal edges of the film are sealedtogether to form a “lap seal” or a “fin seal.” The tube then is pulledvertically downwards to a filling station and collapsed across itstransverse cross-section. The position of such cross-section is at asealing device below the filling station, which makes an air-tighttransverse heat seal at the collapsed portion of the tube.

Next, the flowable material to be packaged enters the tube above thetransverse heat seal, continuously or intermittently, filling the tubeupwardly from the transverse heat seal. The tube is then allowed to dropa predetermined distance usually under the influence of the weight ofthe material in the tube. Depending on the material being packaged andthe packaging process, the jaws of the sealing device are closed again.The tube collapses as a result at a second transverse section that isat, above, or below the air/material interface in the tube. The sealingdevice seals and severs the tube transversely at the second transversesection.

The material-filled portion of the tube is now in the form of a pillowshaped pouch. Thus, the sealing device has sealed the top of the filledpouch, sealed the bottom of the next-to-be-formed pouch and separatedthe filled pouch from the next-to-be-formed pouch, all in one operation.

One VFFS apparatus of the type described above is a Prepac® IS-7E liquidpackaging apparatus. A commonly used sealing device, the so-calledimpulse sealer, has electrically insulated sealing element mounted inthe sealing jaws. In operation, the sealing jaws close andsimultaneously an electrical current flows through the sealing element,for example, a wire. The jaws remain closed while the seal forms, butnot while it cools and solidifies. Therefore, once the sealing jawsopen, the synthetic thermoplastic film must provide a molten trans-verseseal that supports the weight of the flowable material, for example,liquid, in the next-to-be-formed pouch.

For reasons of economy, customers are demanding thinner and thinnerfilms for the pouching of fluids. This can lead to one of two problemsin commercially available film formulations: (1) inadequate sealabilityand toughness, or (2) insufficient stiffness.

Pouches made from commercially available films tend to suffer fromdefective seals, that is, a tendency to have weak transverse end and/orlongitudinal seals even though the operating conditions of the impulsesealer have been optimized. Defective seals may lead to the phenomenonknown as “leakers,” in which the flowable material, for example, milk,may escape from the pouch through pinholes that develop at or close tothe seal. It has been estimated that leakers account for about 1-2% ofthe 1.3 liter milk pouch production.

As the pouch film is down-gauged for reasons of economy, its stiffnessmay also become an issue. Lack of stiffness may adversely affect therunnability of the film on a form, fill and seal apparatus and give poorstand-up properties for pouches in, for instance, a milk pitcher.However, higher stiffness has traditionally required a thicker gauge ofthe pouch film. But thicker gauge requires more material. The presentinvention, by localizing the stiffening material towards the outside ofthe multi-layer film, addresses both these issues in that the stiffnessof the multi-layer film is not adversely affected even when its gaugethickness is reduced.

SUMMARY

The present invention relates to a multi-layer film for making pouchesfor containing flowable materials, said multi-layer film comprising thefollowing layers in order, from an at least one inner sealant-layer toan at least one outer sealant-layer:

(A) said at least one inner sealant-layer comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(B) a first at least one interposed layer adjacent to said at least oneinner sealant-layer, said first at least one interposed layercomprising:

(i) an at least one polypropylene interpolymer (“PI”) and an at leastone polymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(B)(i)(b);

wherein the centerline of said first at least one interposed layer iscloser to the centerline of said at least one inner sealant-layer thanto the centerline of said multi-layer film;

(C) at least one core layer, adjacent to said first at least oneinterposed layer, said at least one core layer comprising polyethylenethat is selected from the group consisting of:

(i) at least one low-density ethylene-alpha olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(D) a second at least one interposed layer adjacent to said at least onecore layer, said second at least one interposed layer comprising:

(i) an at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(D)(i)(b);

wherein the centerline of said second at least one interposed layer iscloser to the centerline of said at least one outer sealant-layer thanto the centerline of said multi-layer film; and

(E) said at least one outer sealant-layer, comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

wherein said multi-layer film thickness is in the range of from about 35microns to about 66 microns;

wherein a combined thickness of said first at least one interposed layerand said second at least one interposed layer is in the range of fromabout 10% to about 27% of the total thickness of said multi-layer film;

wherein a combined thickness of said inner sealant-layer and said outersealant-layer is in the range of from about 10% to about 27% of thetotal thickness of said multi-layer film.

This invention also relates to a process for making pouches filled witha flowable material, using a vertical form, fill and seal apparatus,wherein each pouch is made from a flat web of film by the followingsteps:

(I) forming a tubular film therefrom with a longitudinal seal andsubsequently flattening said tubular film at a first position;

(II) transversely heat-sealing said tubular film at the flattenedposition;

(III) filling said tubular film with a predetermined quantity offlowable material above said first position;

(IV) flattening said tubular film above the predetermined quantity offlowable material at a second position; and

(V) transversely heat sealing said tubular film at said second position,wherein said pouches are made from a flat web of film made from amulti-layer film, comprising the following layers in order of an atleast one inner sealant-layer to an at least one outer sealant-layer:

(A) said at least one inner sealant-layer comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(B) a first at least one interposed layer adjacent to said at least oneinner sealant-layer, said first at least one interposed layercomprising:

(i) an at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(B)(i)(b);

wherein the centerline of said first at least one interposed layer iscloser to the centerline of said at least one inner sealant-layer thanto the centerline of said multi-layer film;

(C) at least one core layer, adjacent to said first at least oneinterposed layer, said at least one core layer comprising polyethylenethat is selected from the group consisting of:

(i) at least one low-density ethylene-alpha olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(D) a second at least one interposed layer adjacent to said at least onecore layer, said second at least one interposed layer comprising:

(i) an at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(D)(i)(b);

wherein the centerline of said second at least one interposed layer iscloser to the centerline of said at least one outer sealant-layer thanto the centerline of said multi-layer film; and

(E) said at least one outer sealant-layer, comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

wherein said multi-layer film thickness is in the range of from about 35microns to about 66 microns;

wherein a combined thickness of said first at least one interposed layerand said second at least one interposed layer is in the range of fromabout 10% to about 27% of the total thickness of said multi-layer film;

wherein a combined thickness of said inner sealant-layer and said outersealant-layer is in the range of from about 10% to about 27% of thetotal thickness of said multi-layer film; and

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A shows a general schematic of the multilayer film of the presentinvention. FIG. 1 B shows a multilayer film of the present inventionhaving layers of different thicknesses in comparison to FIG. 1 A.

FIG. 2 shows the schematic of interposed layer having multiple layerswith varying concentrations of the polypropylene polymer.

FIG. 3 shows DSC melting peak in the region 160-165.degree. C. forisotactic polypropylene homopolymer (“homoPP”).

FIG. 4 shows DSC melting curve for a homogeneous propylene-ethyleneinterpolymer (“HOPI”).

FIG. 5 shows the third-phase DSC melting peak in the 120-125.degree. C.region of a heterogeneous polypropylene interpolymer, wherein thecomonomer is ethylene (“HEPI”).

FIG. 6 shows the DSC melting curve for a heterogeneous LLDPE polymerpolymerized using a traditional Zeigler-Natta catalyst.

FIG. 7 shows the DSC melting curve for a homogeneous LLDPE polymerpolymerized using a single site catalyst.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS Definitions

All percentages expressed in the present patent application are byweight of the total weight of the composition unless expressedotherwise.

All ratios expressed in this patent application are on a weight:weightbasis unless expressed otherwise.

In this patent application, ranges are used as shorthand only to avoidlisting and describing each and every value within the range. Anyappropriate value within the range can be selected as the upper value,the lower value, or the end-point of the range.

In this patent application, the singular form of a word includes itsplural, and vice versa, unless the context clearly dictates otherwise.Thus, references “a,” “an,” and “the” generally include the plurals ofthe respective terms they qualify. For example, reference to “a method”includes its plural—“methods.” Similarly, the terms “comprise,”“comprises,” and “comprising,” whether used as a transitional phrase inthe claims or otherwise, should be interpreted inclusively rather thanexclusively. Likewise the terms “include,” “including,” and “or” shouldbe construed to be inclusive, unless such a construction is clearlyprohibited from the context. Similarly, the term “examples,”particularly when followed by a listing of terms, is merely exemplaryand illustrative and should not be deemed to be exclusive orcomprehensive.

The methods, compositions, and other advances disclosed in this patentapplication are not limited to particular methodology, protocols, andreagents described in the application because, as the skilled artisanwill appreciate, they may vary. Further, the terminology used in thisapplication describes particular embodiments only, and should not beconstrued as limiting the scope of what is disclosed or claimed.

Unless defined otherwise, all technical and scientific terms, terms ofart, and acronyms used in the present application have the meaningscommonly understood by one of ordinary skill in the art in the field(s)of the invention, or in the field(s) where the term is used. Althoughany compositions, methods, articles of manufacture, or other means ormaterials similar or equivalent to those described in the present patentapplication can be used in the practice of the present invention,specific compositions, methods, articles of manufacture, or other meansor materials are described only for exemplification.

All patents, patent applications, publications, technical and/orscholarly articles, and other references cited or referred to in thispatent application are incorporated in their entirety by reference tothe extent allowed by law. The discussion of those references isintended merely to summarize the assertions made in these references. Noadmission is made that any such patents, patent applications,publications or references, or any portion thereof, are relevant,material, or prior art. The right to challenge the accuracy andpertinence of any assertion of such patents, patent applications,publications, and other references as relevant, material, or prior artis specifically reserved.

GENERAL INVENTION

As used herein, the term “flowable material” does not include gaseousmaterials, but encompasses materials which are flowable under gravity ormay be pumped. Such materials include liquids, for example, milk, water,fruit juice, oil; emulsions, for example, ice cream mix, soft margarine;pastes, for example, meat pastes, peanut butter; preserves, for example,jams, pie fillings, marmalade; jellies; doughs; ground meat, forexample, sausage meat; powders, for example, gelatin powders,detergents; granular solids, for example, nuts, sugar; and likematerials. The invention described herein is particularly useful forflowable foods such as milk. In addition, as used herein “density” isdetermined by ASTM Procedure D 1505-85, “stiffness” is understood to betensile modulus of elasticity as measured by ASTM Procedure D 882-91(Method A) and “melt-index” by ASTM Procedure D 1238-90B (Condition Efor polyethylene and Condition L for most polypropylenes). The “meltingpoint” of a polymer is measured as the peak melting point whenperforming differential scanning calorimetry (DSC) as described in ASTMProcedure D 3417-83 (rev. 88).

In one embodiment, this invention relates to polyethylene-basedmulti-layer films usable for pouch-making for containing of flowablematerials. More specifically, this invention provides a multi-layer filmthat is lower in gauge (thickness) but retains an adequate combinationof stiffness and toughness for its use in pouches for flowablematerials.

In one embodiment, the polyethylene-based multi-layer film comprisesfive layers (FIG. 1): an inner sealant-layer (1), a first interposedlayer (2), a core layer (3), a second interposed layer (4), and theouter sealant-layer (5). The interposed layer comprises a stiffpolymer-polypropylene (“PP”). Moreover, a combined thickness of thefirst and the second interposed layer is in the range of from about 10%to about 27% of the total thickness of the multi-layer film. Similarly,a combined thickness of the inner and outer sealant-layers is also inthe range of from about 10% to about 27% of the total thickness of themulti-layer film. Stated another way, the core layer thickness rangesfrom about 46% (See FIG. 1A) to about 80% (see FIG. 1B) of the totalthickness of the multi-layer film. Because generally, the PP islocalized in the interposed layer and not distributed across themulti-layer film of the present invention, and because of the rangelimitations on the sealant layers and the interposed layers, the PPresides much closer to the center-line of the inner and the outersealant-layers than to the centerline of the multi-layer film. As aresult, the multi-layer film of the present invention provides alowering of the gauge at a performance substantially similar to thosefilms that are higher in their gauge. A PP film cannot be used on itsown for fluid packaging because, for example, it lacks the requiredsealing and toughness properties. Moreover, if the PP is distributedthroughout the pouch-making film, it renders the film hazy and unclear,and requires the use of a compatibilizer throughout the film as well tobond to the polyethylene phase. However, clear film is desired forexample for making milk pouches. The present invention thus addressesall these issues.

This invention also relates to a process for making such multi-layerfilms and to pouches made from such multi-layer films.

More specifically, in one embodiment, the present invention relates to apolyethylene based multi-layer film that is from about 35 microns toabout 66 microns thick, for making pouches for containing flowablematerials. The multi-layer film comprises the following layers: an atleast one inner sealant-layer, a first at least one interposed layer, anat least one core layer, a second at least one interposed layer, and anat least one outer sealant-layer, in order, from an at least one innersealant-layer to an at least one outer sealant-layer; wherein:

(A) said at least one inner sealant-layer and/or said at least one outersealant-layer comprises polyethylene that is selected from the groupconsisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

wherein a combined thickness of said inner sealant-layer and said outersealant-layer is in the range of from about 10% to about 27% of thetotal thickness of said multi-layer film;

(B) the first and/or the second at least one interposed layer isadjacent to said at least one inner sealant-layer or outersealant-layer, respectively, and said first and/or the second at leastone interposed layer comprises:

(i) at least one polypropylene interpolymer and at least one polymericcompatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or \

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(B)(i)(b);

wherein the centerline of said first and/or the second at least oneinterposed layer is closer to the centerline of said at least one innersealant-layer or at least one outer sealant layer, respectively, than tothe centerline of said multi-layer film;

wherein a combined thickness of said first at least one interposed layerand said second at least one interposed layer is in the range of fromabout 10% to about 27% of the total thickness of said multi-layer film;and

(C) said at least one core layer, adjacent to said first at least oneinterposed layer, comprises polyethylene that is selected from the groupconsisting of:

(i) at least one low-density ethylene-alpha olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process.

In a preferred embodiment, the multi-layer film thickness is in therange of from about 38 microns to about 63 microns. In a furtherpreferred embodiment, the multi-layer film thickness is in the range offrom about 44 microns to about 60 microns. In another preferredembodiment, the multi-layer film thickness is in the range of from about47 microns to about 59 microns. In yet another embodiment, themulti-layer film thickness is selected from the group consisting ofabout 33 microns, about 34 microns, about 35 microns, about 36 microns,about 37 microns, about 38 microns, about 39 microns, about 40 microns,about 41 microns, about 42 microns, about 43 microns, about 44 microns,about 45 microns, about 46 microns, about 47 microns, about 48 microns,about 49 microns, about 50 microns, about 51 microns, about 52 microns,about 53 microns, about 54 microns, about 55 microns, about 56 microns,about 57 microns, about 58 microns, about 59 microns, about 60 microns,about 61 microns, about 62 microns, about 63 microns, about 64 microns,and about 66 microns. In a further preferred embodiment, said combinedfilm thickness can be a number (integer or non-integer) between any twointeger numbers between and including 33 microns and 66 micronsidentified supra. For example, the combined thickness can be about 33.1microns, about 33.2 microns, about 33.3 microns, about 33.4 microns,about 33.5 microns, about 33.6 microns, about 33.7 microns, about 33.8microns, about 33.9 microns, and so on and so forth.

In a preferred embodiment, the combined thickness of said first at leastone interposed layer and said second at least one interposed layer is inthe range of from about 10% to about 27% of the total thickness of saidmulti-layer film. In a preferred embodiment, the multi-layer filmthickness is selected from the group consisting of about 10%, about 11%,about 12%, about 13%, about 14%, about 15%, about 16%, about 17% s,about 18%, about 19%, about 20%, about 21% s, about 22%, about 23%,about 24%, about 25%, about 26%, and about 27%. In a preferredembodiment, said combined film thickness can be a number (integer ornon-integer) between any two integer numbers between and including 10%and 27% identified supra. For example, the combined thickness can beabout 10.1%, about 10.2%, about 10.3%, about 10.4%, about 10.5%, about10.6%, about 10.7%, about 10.8%, about 10.9%, and so on and so forth.

Similarly, in a preferred embodiment, the combined thickness of saidinner and said outer sealant layers is in the range of from about 10% toabout 27% of the total thickness of said multi-layer film. In apreferred embodiment, the multi-layer film thickness is selected fromthe group consisting of about 10%, about 11%, about 12%, about 13%,about 14%, about 15%, about 16%, about 17% s, about 18%, about 19%,about 20%, about 21% s, about 22%, about 23%, about 24%, about 25%,about 26%, and about 27%. In a preferred embodiment, said combined filmthickness can be a number (integer or non-integer) between any twointeger numbers between and including 10% and 27% identified supra. Forexample, the combined thickness can be about 10.1%, about 10.2%, about10.3%, about 10.4%, about 10.5%, about 10.6%, about 10.7%, about 10.8%,about 10.9%, and so on and so forth.

The Inner and the Outer Sealant-Layer

In one embodiment, the multi-layer film comprises an at least one innersealant layer, and an at least one outer sealant layer. The innersealant layer is externally on one side of the multi-layer film, and theouter sealant layer is externally on the other side of the multi-layerfilm.

The multi-layer film comprises one inner sealant layer or more than oneinner sealant-layers. For example, the multi-layer film can have two,three, or four inner sealant-layers stacked adjacent to each other.Similarly, the multi-layer film comprises one outer sealant layer ormore than one outer sealant layers. For example, the multi-layer filmcan have two, three, or four outer sealant layers.

While it may be preferred that the inner sealant-layer and the outersealant layer thicknesses are approximately the same, in other preferredembodiments, their thicknesses may not be the same.

Also, while it is preferred that the multi-layer film of the presentinvention comprises the same number of inner sealant-layers and theouter sealant layers, in other embodiments, the number of inner sealantlayers may be different from the number of outer sealant layers.

For this invention, the total combined thickness of said at least oneinner sealant layer and said at least one outer sealant layer is fromabout 10% to about 27% of the total thickness of the multi-layer film.In other embodiments of the invention, the total combined thickness ofthe sealant layers can be about 11%, about 12%, about 13%, about 14%,about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about21%, about 22%, about 23%, about 24%, about 25%, about 26% and about27%, of the total thickness of the multi-layer film. The total combinedthickness of the sealant layers can also be intermediate percentagebetween the percentages cited supra—for example, a total combinedthickness that is from about 11.1%, 11.2%, 11.3%, 11.4%, and so on andso forth between other percentages cited.

The at least one inner sealant-layer and the at least one outersealant-layer comprise polyethylene that is selected from the groupconsisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process.

The ethylene homopolymer used in the at least one inner sealant layer orin the at least one outer sealant layer, in one embodiment, is made in ahigh-pressure polymerization process. One or more ethylene homopolymerscan be used in the at least one inner sealant layer or in the at leastone outer sealant layer. In one embodiment, the weight percent of theethylene homopolymer is from 0 to about 15 parts by weight of said atleast one inner sealant layer or said at least one outer sealant layer.In other embodiments, the weight percent range of the ethylenehomopolymer can be defined by any two numbers from about 0.0, about 0.5,about 1.0, about 1.5, about 2.0, about 2.5, about 3.0, about 3.5, about4.0. about 4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0,about 7.5, about 8.0, about 8.5, about 9.0, about 9.5, about 10.0, about10.5, about 11.0, about 11.5, about 12.0, about 12.5, about 13.0, about13.5, about 14.0, about 14.5, and about 15.0 parts by weight of said atleast one inner sealant layer or said at least one outer sealant layer.The ethylene homopolymer has a density in the range of from about 0.918to about 0.923 g/cm.sup.3, and a melt-index in the range of from about0.1 to about 1.1 dg/min. In other embodiments, the ethylene homopolymerdensity range can be defined by any two numbers, namely, about 0.918,about 0.919, about 0.920, about 0.921, about 0.922, and about 0.923g/cm.sup.3, Similarly, the melt-index range can also be defined by anytwo numbers, namely, about 0.1, about 0.2, about 0.3, about 0.4, about0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, and 1.1dg/min.

In another embodiment, more than one ethylene homopolymers may be usedin one or more layers of the inner sealant layer or the outer sealantlayers. The number of ethylene homopolymers and the type of ethylenehomopolymers may vary between any two inner sealant layers or the outersealant layers. For example, a multi-layer film comprises three innersealant-layers (I1, I2, and I3) and three outer sealant layers (O1, O2,and O3). In one embodiment, I1, I2, and I3, and O1, O2, and O3, forexample, may have only one and the same ethylene homopolymer. In anotherembodiment, I1, I2, and I3 may have the same ethylene homopolymer, butdifferent from O1, O2, and O3. In another embodiment, for example, I1may have two ethylene homopolymers while I2 may have three ethylenehomopolymers, while I3 may have no ethylene homopolymer. Two ethylenehomopolymers may differ from each other by having different densities,different melt-indices, different molecular weights, or different branchstructures.

The ethylene copolymer used in the at least one inner sealant layer orin the at least one outer sealant layer, in one embodiment, is made in ahigh-pressure polymerization process. One or more ethylene copolymerscan be used in the at least one inner sealant layer or in the at leastone outer sealant layer. In one embodiment, the weight percent of theethylene homopolymer is from 0 to about 15 parts by weight of said atleast one inner sealant layer or said at least one outer sealant layer.In other embodiments, the weight percent range of the ethylenehomopolymer can be defined by any two numbers from about 0.0, about 0.5,about 1.0, about 1.5, about 2.0, about 2.5, about 3.0, about 3.5, about4.0. about 4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0,about 7.5, about 8.0, about 8.5, about 9.0, about 9.5, about 10.0, about10.5, about 11.0, about 11.5, about 12.0, about 12.5, about 13.0, about13.5, about 14.0, about 14.5, and about 15.0 parts by weight. Theethylene copolymer has a density in the range of from about 0.930 toabout 0.960 g/cm.sup.3, and a melt-index in the range of from about 0.1to about 10 dg/min. The density range can also be defined by any twonumbers from about 0.930, about 0.931, . . . , about 0.958, about 0.959,and about 0.960 g/cm.sup.3.

In another embodiment, more than one ethylene copolymers may be used inone or more layers of the inner sealant layer or the outer sealantlayers. The number of ethylene copolymers and the type of ethylenecopolymers may vary between any two inner sealant layers or the outersealant layers. For example, a multi-layer film comprises three innersealant-layers (I1, I2, and I3) and three outer sealant layers (O1, O2,and O3). In one embodiment, I1, I2, and I3, and O1, O2, and O3, forexample, may have only one and the same ethylene copolymer. In anotherembodiment, I1, I2, and I3 may have the same ethylene copolymer, butdifferent from O1, O2, and O3. In another embodiment, for example, I1may have two ethylene copolymers while I2 may have three ethylenecopolymers, while I3 may have no ethylene copolymer. Two ethylenecopolymers may differ from each other by having different densities,different melt-indices, different molecular weights, or different branchstructures.

The comonomer of ethylene in the ethylene copolymer described in theforegoing can be chosen from polar monomers such as vinyl acetate,acrylic acid, methacrylic acid, and vinyl methacrylate, wherein theethylene copolymer is manufactured in a high-pressure polymerizationprocess. The concentration of polar comonomer must be kept relativelylow in order that the copolymer has good compatibility with the majorpolyethylene component of the sealant layer(s). For example, ethylenevinyl acetate copolymers should contain less than or equal to 15 wt %vinyl acetate. Otherwise, poor optical appearance, and even poorintra-layer adhesion, can result.

In another embodiment, the at least one inner sealant layer or the atleast one outer sealant layer comprises at least one low-densityethylene-alpha-olefin copolymer, which may be found alone or in a blendform with an ethylene homopolymer described supra, or ethylene copolymerdescribed supra. Such low-density ethylene alpha-olefin copolymer, in apreferred embodiment, is found as a copolymer that is from about 80 toabout 98 parts by weight of the at least one inner or the at least oneouter sealant layer weight. The copolymer range can also be defined byany two numbers from about 80, about 81, about 82, . . . , about 96,about 97, and about 98 parts by weight of the at least one inner or theat least one outer sealant layer weight. The copolymer is a low-densitycopolymer of ethylene and an at least one C.sub.4-C.sub.10 alpha-olefinmanufactured in a polymerization process using a single-sitepolymerization catalyst, with a density in the range of from about 0.909to about 0.935 g/cm.sup.3 and a melt-index in the range of from about0.5 to about 1.5 dg/min. The density range can also be defined by anytwo numbers from about 0.909, about 0.910, about 0.911, . . . , about0.933, about 0.934, and about 0.935 g/cm.sup.3. Similarly, themelt-index range can be defined by any two numbers from about 0.5, about0.6, about 0.7, about 0.8, about 0.9, about 1.0, and about 1.1 dg/min.In addition, said embodiment further comprises, from about 0 to about 15parts by weight of an additional at least one low-density copolymer ofethylene and an at least one C.sub.4-C.sub.10 alpha-olefin. In otherembodiments, the weight percent range of the ethylene homopolymer can bedefined by any two numbers from about 0.0, about 0.5, about 1.0, about1.5, about 2.0, about 2.5, about 3.0, about 3.5, about 4.0. about 4.5,about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about 7.5, about8.0, about 8.5, about 9.0, about 9.5, about 10.0, about 10.5, about11.0, about 11.5, about 12.0, about 12.5, about 13.0, about 13.5, about14.0, about 14.5 and about 15.0 parts by weight. Said additional atleast one low-density copolymer is an ultra-low density copolymer ofethylene and said at least one C.sub.4-C.sub.10 alpha-olefin,manufactured in a polymerization process using a single-sitepolymerization catalyst, with a density in the range of from about 0.859to about 0.888 g/cm.sup.3 and a melt-index in the range of from about0.4 to about 0.6 dg/min. The density range can also be defined by anytwo numbers from about 0.859, about 0.860, about 0.861, . . . , about0.886, about 0.887, and about 0.888 g/cm.sup.3. Similarly, themelt-index range can be defined by any two numbers from about 0.4, about0.45, about 0.5, about 0.55, and about 0.6 dg/min.

In another embodiment, the foregoing low-density copolymer of ethyleneand at least one C.sub.4-C.sub.10 alpha-olefin, or said at least oneultra-low density copolymer of ethylene and at least oneC.sub.4-C.sub.10 alpha-olefin is selected from ethylene/butene-1copolymers, ethylene/hexene-1 copolymers, ethylene/octene-1 copolymers,ethylene/octene-1/butene-1 terpolymers and ethylene/hexene-1/butene-1terpolymers.

The C.sub.4-C.sub.10 alpha-olefin also includes the cyclic counterparts.

In a preferred embodiment, the thickness of said at least one sealantlayer is from about 2 microns about 20 microns. The thickness of said atleast one sealant layer can be about 3, about 4, about 5, about 6, about7, about 8, about 9, about 10, about 11, about 12, about 13, about 14,about 15, about 16, about 17, about 18, about 19, or about 20 microns.

The First and the Second Interposed Layer

In one embodiment, the multi-layer film comprises a first at least oneinterposed layer adjacent to an at least one inner sealant layer and toan at least one core layer on the other side, and a second at least oneinterposed layer adjacent to said core layer on the other side of thesaid first at least one interposed layer and adjacent to an at least oneouter sealant layer. The inner sealant layer is externally on one sideof the multi-layer film, and the outer sealant layer is externally onthe other side of the multi-layer film.

The multi-layer film comprises one first interposed layer or more thanone first interposed layers. For example, the multi-layer film can havetwo, three, or four first interposed layers stacked adjacent to eachother. Similarly, the multi-layer film comprises one second interposedlayer or more than one second interposed layers. For example, themulti-layer film can have two, three, or four second interposed layers.

While it may be preferred that the first interposed layer and the secondinterposed layer thicknesses are approximately the same, in otherpreferred embodiments, their thicknesses may not be the same.

Also, while it is preferred that the multi-layer film of the presentinvention comprises the same number of first interposed layers and thesecond interposed layers, in other embodiments, the number of firstinterposed layers may be different from the number of second interposedlayers.

In this invention, the centerline of said first at least one interposedlayer is closer to the centerline of said at least one innersealant-layer than to the centerline of said multi-layer film. If morethan one first interposed layers are present, then reference is made tothe centerline of the combined set of first interposed layers.Similarly, if there is more than one inner sealant layer, then referenceis made to the centerline of the combined set of inner sealant layers.

For this invention, the total combined thickness of said first at leastone interposed layer and said second at least one interposed layer isfrom about 10% to about 27% of the total thickness of the multi-layerfilm. In other embodiments of the invention, the total combinedthickness of the sealant layers can be about 11%, about 12%, about 13%,about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%and about 27%, of the total thickness of the multi-layer film. The totalcombined thickness of the interposed layers can also be intermediatepercentage between the percentages cited supra—for example, a totalcombined thickness that is from about 11.1%, about 11.2%, about 11.3%,about 11.4%, and so on and so forth between other percentages cited.

The first at least one interposed layer and the second at least oneinterposed layer comprise:

(i) at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in (i).

Preferably, the at least one polypropylene interpolymer may be aheterogeneous or homogeneous copolymer of polypropylene, or blend ofcopolymer polypropylenes and homopolymer polypropylenes. The at leastone polypropylene interpolymer is in the range of from about 40 to about95 parts by weight of said first at least one interposed layer or ofsaid second at least one interposed layer. The range can also be definedby any two numbers from about 40, about 41, about 42, . . . , about 93,about 94, and about 95 parts. In one embodiment, to prepare a highimpact strength version of the film the grade of polypropylene or blendof polypropylene(s) used is such that the izod impact strength of the PPis greater than 9 ft-lb.sub.f per inch of notch according to AmericanSociety for Testing and Materials (ASTM) standard D256.

More preferably, a particularly suitable polypropylene may be ablown-film grade, high impact copolymer with an izod impact strength(ASTM D 257, at 23.degree. C.) of from 8 to 80 ft-lb.sub.f per inch ofnotch, and melt flow index (ASTM D 1238, 2.16 kg, 23.degree. C.) of fromabout 0.3 to about 5.5 dg/min. The izod impact strength range can alsobe defined by any two numbers from 8, 9, 10, . . . , 78, 79, and 80ft-lb.sub.f per inch of notch. Similarly, the melt-flow index range canalso be defined by any two numbers from about 0.3, about 0.35, about0.4, about 0.45, . . . , about 5.40, about 5.45, and about 5.50 dg/min.In a preferred embodiment, said at least one polypropylene has amelt-index in the range of from about 0.45 to about 0.75 dg/min.

In another preferred embodiment, said at least one high-densitypolyethylene is in the range of from about 0 to about 50 parts by weightof said first at least one interposed layer or of said second at leastone interposed layer, wherein said at least one high-densitypolyethylene that is manufactured in a polymerization process using asingle-site polymerization catalyst or a Ziegler-Natta catalyst, whereinsaid at least one high-density polyethylene has a density greater than0.935 g/cm.sup.3, but less than 0.970 g/cm.sup.3 and a melt-index in therange of from about 0.75 to about 1.05 dg/min, and said at least onepolymeric compatibilizer is in the range of from about 2 to about 10parts by weight of said first at least one interposed layer or of saidsecond at least one interposed layer. In other embodiments, themelt-index range can be defined by any two numbers from about 0.75,about 0.80, about 0.85, about 0.90, about 0.95, about 1.00, and about1.05 d/min. Similarly, the polymeric compatibilizer range can be definedby any two numbers from about 2, about 3, about 4, about 5, about 6,about 7, about 8, about 9, and about 10 parts by weight of said first atleast one interposed layer or of said second at least one interposedlayer.

In another embodiment, the polymeric compatibilizer is in the range 2 to10% by weight of the first or second at least one interposed layer.Preferably, the polymer compatibilizer may be selected from the groupconsisting of ethylene methacrylate, ethylene methacrylate copolymer(EMAC), ethylene butyl acrylate, ethylene vinyl acetate, ethylenepropylene diamine rubber, ethylene propylene copolymer, ethylene styrenecopolymer, and ethylene thermoplastic elastomers. As one skilled in theart would realize, the higher the proportion of copolymer content in anethylene-copolymer type compatibilizer, the lower the amount ofethylene-copolymer type compatibilizer would be required. Thus by way ofillustrative and non-limiting example, one may use 8% of a 20%methacrylate content EMAC or 7% of 24% methacrylate content EMAC andachieve similar degrees of compatibilization of the polymer blend in theinterposed layer of the multi-layer film. More preferably, saidcompatibilizer may be such as, but not limited to one of ethylenemethacrylate (EMA), EMAC, ethylene vinyl acetate (EVA), ethylenepropylene diamine rubber (EPDM), Versify® (ethylene propylenecopolymer); ethylene styrene copolymer (Index® copolymers), Engage®,Lotryl®, and/or the tie-layer polymers between PP and PE. A 20%methacrylate content EMAC is particularly convenient for use in thisapplication. A particularly preferred compatibilizer is ethylenemethacrylate copolymer with 20% or more of methacrylate content.Advantageously, when the polymer compatibilizer comprises EMAC, it mayhave from 10 to 25% of methacrylate content. In other embodiments, themethacrylate content range can be defined by any two numbers from about10, about 11, about 12, . . . , about 23, about 24, and about 25%.

A material that works as a compatibilizer often also works as tie-layerresin. Any tie-layer polymer well known to a person skilled in the artas appropriate to bind PP with PE may be used. Preferably, saidtie-layer polymers may be selected from the group consisting of EMA,EMAC, EVA, EPDM, Versify®; ethylene styrene copolymer (Index®copolymers), Engage®, Lotryl®, other functional copolymers orterpolymers, other ethylene propylene copolymers; anhydride- or maleicanhydride-modified linear low-density polyethylene, modified ethyleneacrylate carbon monoxide terpolymers, and ethylene ethyl acrylatecopolymer (EEA). A particularly preferred tie-layer resin is ethylenemethacrylate copolymer with 20% or more of methacrylate content.

In another embodiment, the first or the second at least one interposedlayers comprises a first at least one ethylene-alpha olefin copolymer.The ethylene-alpha olefin copolymer is in the range of from about 0 toabout 15 parts by weight of said first at least one interposed layer orof said second at least one interposed layer. The copolymer is anultra-low-density copolymer of ethylene and an at least oneC.sub.4-C.sub.10 alpha-olefin manufactured in a polymerization processusing a single-site polymerization catalyst, with a density in the rangeof from about 0.859 to about 0.905 g/cm.sup.3 and a melt-index in therange of from about 0.4 to about 1.1 dg/min. The density range can alsobe defined by any two numbers from about 0.859, about 0.860, about0.861, . . . , about 0.903, about 0.904, and about 0.905 g/cm.sup.3.Similarly, the melt-index range can be defined by any two numbers fromabout 0.4, about 0.45, about 0.5, . . . , about 0.95, about to, about1.05 and about 1.1 dg/min.

In another embodiment, the second ethylene-alpha-olefin copolymer is inthe range of from about 0 parts to 15 parts by weight, and can bemanufactured in a polymerization process using either a single-site orZeigler-Natta polymerization catalyst, wherein said copolymer has adensity in the range of from about 0.909 to about 0.935 g/cm.sup.3 and amelt-index in the range of from about 0.5 to about 1.5 dg/min. In otherembodiments, the weight percent range of the secondethylene-alpha-olefin copolymer can be defined by any two numbers fromabout 0.0, 0.5, about 1.0, about 1.5, about 2.0, about 2.5, about 3.0,about 3.5, about 4.0. about 4.5, about 5.0, about 5.5, about 6.0, about6.5, about 7.0, about 7.5, about 8.0, about 8.5, about 9.0, about 9.5,about 10.0, about 10.5, about 11.0, about 11.5, about 12.0, about 12.5,about 13.0, about 13.5, about 14.0, about 14.5 and about 15.0 parts byweight. The density range can also be defined by any two numbers fromabout 0.909, about 0.910, about 0.911, . . . , about 0.933, about 0.934,and about 0.935 g/cm.sup.3. Similarly, the melt-index range can bedefined by any two numbers from about 0.5, about 0.55, about 0.60, . . ., about 1.40, about 1.45, and about 1.50-dg/min. The secondethylene-alpha-olefin copolymer is not the same as the first at leastone ethylene-alpha olefin copolymer described supra.

In another embodiment, the foregoing low-density copolymer of ethyleneand at least one C.sub.4-C.sub.10 alpha-olefin, or said at least oneultra-low density copolymer of ethylene and at least oneC.sub.4-C.sub.10 alpha-olefin is selected from ethylene/butene-1copolymers, ethylene/hexene-1 copolymers, ethylene/octene-1 copolymers,ethylene/octene-1/butene-1 terpolymers and ethylene/hexene-1/butene-1terpolymers.

The C.sub.4-C.sub.10 alpha-olefin also includes the cyclic counterparts.

The first interposed layer and/or the second interposed layer maycomprise more than one interposed layer. In one embodiment, the PPdistribution will be different between the different interposed layersof the first and/or the second interposed layer in such a way that thePP concentration by its percent weight of the total weight of thespecific interposed layer, increases as from the innermost interposedlayer (that layer which is more proximate to the core layer) to theoutermost interposed layer (that layer which is more proximate to thesealant layers. This embodiment is schematically described in FIG. 2. InFIG. 2, a multi-layer film is shown. The first and the second interposedlayers, each, comprise four layers (F1, F2, F3, F4 and S1, S2, S3, S4,respectively). F1 and S1 are layers most proximate to the core layer C.Similarly, F4 and S4 are proximate to the inner sealant-layer (I) andthe outer sealant layer (O). F1, for example, has 50% of PP, F2 has 70%of PP, F3 has 85% PP and F4 has 95% PP, with the added restriction thatthe overall concentration of PP in the first and in the secondinterposed layers must be about 40 to about 95 wt %. In otherembodiments, the range of first component polypropylene can be definedby any two numbers from about 40, about 41, about 42, . . . , about 93,about 94, and about 95 wt %. Similarly, the second interposed layersS1-S4 can also have varying amounts of PP, increasing in concentrationfrom 51 to S4.

In one embodiment, the thickness of the first interposed layers, forexample, F1, F2, F3, and F4 is different. Similarly, the thickness ofthe second interposed layers, S1, S2, S3, and S4 can also be different.

In a preferred aspect of the invention relates to the fact that the useof the compatibilizer such as EMAC make the film blend more supple andpliable. This increased suppleness is due to the fact that thefunctional group on the compatibilizer is more bulky than the usualethylene or propylene group. Thus introduction of this polymer into theresin blends causes the crystallized polymer in the film to be moreopen, and indeed, somewhat less crystalline. The net result is—allthings being equal—a film that is more supple when certaincompatibilizers such as for example EMAC, is/are incorporated in thefilm. This contributes to improved film machinability; since it allowsit to pass over structures, such as the tube former or more specificallythe “forming shoulders” in the VFFS machine without becoming permanentlycreased. Films with high levels of PP in PP-HDPE or PP-LLDPE blends tendto crease and “stress-whiten” when folded. The tendency for thispermanent defect to occur in folded film is markedly less when acompatibilizer such as EMAC is included in the resin blend. Itsincorporation “softens” the film without compromising unduly thestrength and stiffness of the film.

In another preferred embodiment, the invention relates to theintroduction of a clarifier either by the use of pre-clarified PP grade,or by separate addition, to create a clear film even when high levels ofPP are present in the blend. A clearer film is desirable for thepackaging of milk, liquids, and/or other flowables. The clearer filmoffers the consumer and packager an opportunity to assess productquality by eye. The clarifier improves the aesthetic appeal of the filmwithout compromising the physical properties of the film. The mechanismof clarification requires that the PP layer is nucleated to such anextent that many small PP spherulites are produced upon cooling asopposed to fewer spherulites than can grow to create larger particles ofPP or PP-PE blends.

A person skilled in the art will know which polypropylene clarifiersand/or nucleating agents are suitable for use. Preferably, suchclarifier may be selected from the group consisting of 4-biphenylcarboxylic acid, thymine, talc, sodium benzoate ordibenzylidene-sorbitol (DBS), bis (p-methyl-dibenzylidene sorbitol)(MDBS) and related sorbitol derivatives. The amount of clarifier thatmay be preferably typically used is in the range of 0.05 to 0.5% byweight of the first or second at least one interposed layer. In otherembodiments, the clarifier amount range can be defined by any twonumbers from about 0.05, about 0.1, about 0.15, . . . , 0.40, 0.45, and0.50% by weight.

In a preferred embodiment, the thickness of said at least one interposedlayer is from about 2 microns about 20 microns. The thickness of said atleast one interposed layer can be about 3, about 4, about 5, about 6,about 7, about 8, about 9, about 10, about 11, about 12, about 13, about14, about 15, about 16, about 17, about 18, about 19, or about 20microns.

Core Layer

The multi-layer film comprises at least one core layer that is adjacentto the first at least one interposed layer on one side and the second atleast one interposed layer on the opposite side. The core layercomprising polyethylene that is selected from the group consisting of:

(i) at least one low-density ethylene-alpha olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

The ethylene homopolymer used in the at least one core layer, in oneembodiment, is made in a high-pressure polymerization process. One ormore ethylene homopolymers can be used in the core layer. In oneembodiment, the weight percent of the ethylene homopolymer is from 10 toabout 50 parts by weight of said at least one core layer. In otherembodiments the weight percent of the ethylene homopolymer range isdefined by any two numbers from about 10, about 11, about 12, . . . ,about 48, about 49, and about 50 parts by weight of said at least onecore layer. The ethylene homopolymer has a density in the range of fromabout 0.918 to about 0.923 g/cm.sup.3, and a melt-index in the range offrom about 0.1 to about 1.1 dg/min. The density range can also bedefined by any two numbers from about 0.918, about 0.919, about 0.920,about 0.921, about 0.922, and about 0.923 g/cm.sup.3. Similarly, themelt-index range can also be defined by any two numbers, namely, about0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7,about 0.8, about 0.9, about 1.0, and 1.1 dg/min.

In another embodiment, more than one ethylene homopolymers may be usedin one or more layers of the core layer. The number of ethylenehomopolymers and the type of ethylene homopolymers may vary between anycore layers. For example, a multi-layer film comprises three core layers(C1, C2, and C3). In one embodiment, C1, C2, and C3, for example, mayhave only one and the same ethylene homopolymer. In another embodiment,C1, C2, and C3 may have the same ethylene homopolymer. In anotherembodiment, for example, C1 may have two ethylene homopolymers while C2may have three ethylene homopolymers, while C3 may have no ethylenehomopolymer. Two ethylene homopolymers may differ from each other byhaving different densities, different melt-indices, different molecularweights, or different branch structures.

The ethylene copolymer used in the at least one core layer, in oneembodiment, is made in a high-pressure polymerization process. One ormore ethylene copolymers can be used in the at least one core layer. Inone embodiment, the weight percent of the ethylene homopolymer is from10 to about 50 parts by weight of said at least one inner sealant layeror said at least one outer sealant layer. The ethylene copolymer has adensity in the range of from about 0.930 to about 0.960 g/cm.sup.3, anda melt-index in the range of from about 0.1 to about 10 dg/min. Thedensity range can also be defined by any two numbers from about 0.930,about 0.935, about 0.940, about 0.945, about 0.950, about 0.955, andabout 0.960 g/cm.sup.3. Similarly, the melt-index range can also bedefined by any two numbers, namely, about 0.1, about 0.2, about 0.3, . .. , about 9.8, about 9.9, and about 10.0 dg/min.

In another embodiment, more than one ethylene copolymers may be used inone or more layers of the core layers. The number of ethylene copolymersand the type of ethylene copolymers may vary between any two corelayers. For example, a multi-layer film comprises three core layers (C1,C2, and C3). In one embodiment, C1, C2, and C3, for example, may haveonly one and the same ethylene copolymer. In another embodiment, forexample, C1 may have two ethylene copolymers while C2 may have threeethylene copolymers, while C3 may have no ethylene copolymer. Twoethylene copolymers may differ from each other by having differentdensities, different melt-indices, different molecular weights, ordifferent branch structures.

The comonomer of ethylene in the ethylene copolymer described in theforegoing can be chosen from polar monomers such as vinyl acetate,acrylic acid, methacrylic acid, and vinyl methacrylate, wherein theethylene copolymer is manufactured in a high-pressure polymerizationprocess. The concentration of polar comonomer must be kept relativelylow in order that the copolymer has good compatibility with the majorpolyethylene component of the sealant layer(s). For example, ethylenevinyl acetate copolymers should contain less than or equal to 15 wt %vinyl acetate. Otherwise, poor optical appearance, and even poorintra-layer adhesion, can result.

In another embodiment, the at least one core layer comprises at leastone low-density ethylene-alpha-olefin copolymer, which may be foundalone or in a blend form with an ethylene homopolymer described supra,or ethylene copolymer described supra. Such low-density ethylenealpha-olefin copolymer, in a preferred embodiment, is found as acopolymer that is from about 35 to about 85 parts by weight of the atleast one core layer weight. The copolymer range can also be defined byany two numbers from about 35, about 36, about 37, . . . , about 83,about 84, and about 85 parts by weight of the at least one core layerweight. The copolymer is a low-density copolymer of ethylene and an atleast one C.sub.4-C.sub.10 alpha-olefin manufactured in a polymerizationprocess using a single-site polymerization catalyst, with a density inthe range of from about 0.909 to about 0.935 g/cm.sup.3 and a melt-indexin the range of from about 0.5 to about 1.5 dg/min. The density rangecan also be defined by any two numbers from about 0.909, about 0.910,about 0.911, . . . , about 0.933, about 0.934, and about 0.935g/cm.sup.3. Similarly, the melt-index range can be defined by any twonumbers from about 0.5, about 0.6, about 0.7, . . . , about 1.3, about1.4, and about 1.5 dg/min. In addition, said embodiment furthercomprises, from about 0 to about 15 parts by weight of an additional atleast one low-density copolymer of ethylene and an at least oneC.sub.4-C.sub.10 alpha-olefin. In other embodiments, the weight percentrange can be defined by any two numbers from about 0.0, 0.5, about 1.0,about 1.5, about 2.0, about 2.5, about 3.0, about 3.5, about 4.0. about4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about 7.5,about 8.0, about 8.5, about 9.0, about 9.5, about 10.0, about 10.5,about 11.0, about 11.5, about 12.0, about 12.5, about 13.0, about 13.5,about 14.0, about 14.5 and about 15.0 parts. Said additional at leastone low-density copolymer is an ultra-low density copolymer of ethyleneand said at least one C.sub.4-C.sub.10 alpha-olefin, manufactured in apolymerization process using a single-site polymerization catalyst, witha density in the range of from about 0.859 to about 0.905 g/cm.sup.3 anda melt-index in the range of from about 0.4 to about 1.1 dg/min.Similarly, the density range can also be defined by any two numbers fromabout 0.859, about 0.860, about 0.861, . . . , about 0.903, about 0.904,and about 0.905 g/cm.sup.3. Similarly, the melt-index range can bedefined by any two numbers from about 0.4, about 0.45, about 0.50, . . ., about 1.0, about 1.05, and about 1.10 dg/min.

In another embodiment, the foregoing low-density copolymer of ethyleneand at least one C.sub.4-C.sub.10 alpha-olefin, or said at least oneultra-low density copolymer of ethylene and at least oneC.sub.4-C.sub.10 alpha-olefin is selected from ethylene/butene-1copolymers, ethylene/hexene-1 copolymers, ethylene/octene-1 copolymers,ethylene/octene-1/butene-1 terpolymers and ethylene/hexene-1/butene-1terpolymers.

The C.sub.4-C.sub.10 alpha-olefin also includes the cyclic counterparts.

Therefore generally, the present invention also provides a multilayerfilm formed from a layer of a sealant film and a layer of a film havinga higher stiffness than the sealant layer, said layer of higherstiffness being formed from a polymer blend involving polypropylene,polyethylene and a polymeric compatibilizer.

In preferred embodiments of the multilayer film of the presentinvention, the film has a stiffness of at least 20 000 psi(approximately 135 MPa), and especially at least 25 000 psi(approximately 170 MPa). In other embodiments, the multilayer film has astiffness of at least 21,000 psi, 22,000 psi, 23,000 psi, or 24,000 psi.

The present invention also provides a pouch containing a flowablematerial, said pouch being made from the previously describedmulti-layer film in tubular form and having transversely heat sealedends.

The present invention further provides a process for making pouchesfilled with a flowable material, using a vertical form, fill and seal(“VFFS”) apparatus, in which process each pouch is made from a flat webof film by forming a tubular film therefrom with a longitudinal seal andsubsequently flattening the tubular film at a first position andtransversely heat sealing said tubular film at the flattened position,filling the tubular film with a predetermined quantity of flowablematerial above said first position, flattening the tubular film abovethe predetermined quantity of flowable material at a second position andtransversely heat sealing said tubular film at the second position, theimprovement comprising making the pouches from a flat web of a film madefrom a multilayer film described previously. The VFFS processes and itsmodifications are described in U.S. Pat. No. 5,538,590 and areincorporated by reference herein in their entirety.

Although melt-index ranges are specified herein, it is understood thatthe polymers have melt indices typical of film-grade polymers.

The multi-layer films of the present invention have the ability to forma lap seal as well as a fin seal. They also substantially reduce thecurl in the laminate.

Catalysts

In the present invention, linear ethylene based polymers, copolymers,terpolymers, etc. are made using the Ziegler-Natta catalysts,single-site catalysts, the metallocene catalysts, or a combination ofsuch catalysts, depending upon the need for the type of polymer.

High pressure low density polyethylene, or HP-LDPE, was the originalpolyethylene to be polymerized from ethylene monomer. The “highpressure” refers to the rather extreme polymerization processconditions. Generally, “low density” refers to the 0.918-0.930g/cm.sup.3 range of polyethylene densities. The HP-LDPE molecules havecomplex branching patterns, with no easily distinguishable backbone. Thepolymer molecules are composed of a whole network of branches of variouslengths from short to long. The present invention makes use of HP-LDPEpolymers which are relatively high in average molecular weight, in otherwords, low in melt-index (0.1-1.1 dg/min).

Development of the Ziegler-Natta catalysts allowed polyethylene (andpolypropylene) to be polymerized under less extreme conditions, and, inparticular, at lower pressures. The first Zeigler-Natta-catalyzedpolyethylene was distinctly different from HP-LDPE in two ways: themolecules were very linear in nature, with essentially no branches, andthe polyethylene could have a very high density (.about.0.960g/cm.sup.3) because the linear molecules could pack together closely toform extensive crystalline domains in the solid polymer.

High density polyethylene, in general, has a density of at least 0.935g/cm.sup.3 but, in this invention, the HDPE must have a density ofgreater than 0.950 g/cm.sup.3 in order to provide sufficient stiffness,but less than or equal to about 0.970 g/cm.sup.3. In other embodimentsof the invention, the HDPE density is within the range defined by anytwo numbers from about 0.950, about 0.951, about 0.952, . . . , about0.968, about 0.969, and about 0.970 g/cm.sup.3. In addition, the highdensity polyethylene has a melt-index of less than 1.05 dg/min, but morethan 0.3 dg/min. HDPE in the melt-index range of 0.01 to 0.3 dg/min,which is generally classified as high molecular weight high densitypolyethylene, HMW-HDPE, has melt flow characteristics, which areunsuitable in the present invention. In other embodiments, the HDPE hasa melt-index in the range defined by any two numbers from about 0.3,about 0.35, about 0.40, . . . , about 0.95, about 1.00, and about 1.05dg/min.

As the use of Zeigler-Natta catalysts continued, it was discovered thatthe density of the linear polyethylene could be controlled and loweredby introducing a comonomer, in addition to the ethylene, for example,butene, hexene or octene. In fact, any low molecular-weight alpha-olefinsuitably reacts with ethylene and breaks up the regularity of the linearchain development during polymerization—the alpha-olefin double bond atthe end of the molecule opens up as it reacts, allowing the carbons oneither side to become part of the linear back-bone, with the remainderof the alpha-olefin molecule becoming a short side chain. The short sidechain disrupts polymer crystallization and lowers density: the more sidechains that are present, the lower the polymer density.

Processes for the commercial manufacture of linear polyethylene havebeen known for more than thirty years. Such processes may be operated attemperatures above the solubilization temperature of the polymer inwhich event the polymer remains in solution, or the processes may beoperated below the solubilization temperature in which event the polymerremains as a slurry in the polymerization solvent. Processes are alsoknown in which the polymerization is conducted in the gas phase in theabsence of solvent. The catalysts used are frequently based on titaniumand are referred to as coordination catalysts; such catalysts may alsobe described as multi-site catalysts or heterogeneous catalysts. Thepolymer obtained is linear in nature, as opposed to the branched natureof high pressure polyethylene. Linear low density polyethylene isobtained by the co-polymerization of ethylene with at least oneC.sub.4-C.sub.10 alpha-olefin hydrocarbon comonomer, examples of whichinclude butene-1, hexene-1 and octene-1. The linear low densitypolyethylene has a density in the range of 0.909 to 0.935 g/cm.sup.3,preferably 0.912 to 0.930 g/cm.sup.3 and especially in the range of0.912 to 0.926 g/cm.sup.3. In other embodiments, the linear low densitypolyethylene has a density in the range defined by any two numbers fromabout 0.909, about 0.910, about 0.911, . . . , about 0.933, about 0.934,and about 0.935 g/cm.sup.3. In addition the polymer has a melt-index inthe range of 0.3 to 10.0 dg/min, preferably 0.3 to 2.0 dg/min andespecially in the range of 0.5 to 1.5 dg/min. In other embodiments, themelt-index is in the range defined by any two numbers from about 0.3,about 0.4, about 0.5, . . . , about 9.8, about 9.9, and about 10.0dg/min.

Traditional Ziegler-Natta catalysts produce heterogeneous LLDPEpolymers. This is because both the molecular weight and the extent ofcomonomer incorporation vary considerably from molecule to molecule. Theheterogeneity of the Zeigler-Natta polymerized LLDPE polyethylene can bedetected from the relatively broad, multi-peak, DSC melting (orfreezing) curve, as illustrated in FIG. 6. The peak melting is observedat about 125.degree. C. with a lower-temperature broader peak. Highmolecular weight molecules with very little incorporated comonomerproduce the major peak (very similar to the original linear polyethylenehomopolymer). Melting copolymers (with a wide range of molecular weightsand comonomer contents) produce the broader peak. The lowest meltingportion, also known as the grease fraction, comprises lowmolecular-weight molecules. Low molecular-weight molecules incorporatehigher number of comonomers that increases branch concentration. Thegrease fraction lubricates the higher molecular-weight linearpolyethylene, improving its extrudability. As the grease fractionincreases, however, the polymer clumps-together impeding the pelletizedpolymer flow. Therefore, the use of Zeigler-Natta-catalyzed polyethylenehas generally been limited to higher than 0.912 g/cm.sup.3 densitypolymers.

It was theorized that different Zeigler-Natta catalyst sites encouragedgrowth of different types of polymer chains resulting in heterogeneouspolyethylene. Therefore, single site catalysts were developed, whichwould produce homogeneous LLDPE polymers, which were more uniform withrespect to molecular weight distribution and comonomer incorporation.Thus, polyethylene densities as low as 0.880-0.965 g/cm.sup.3 are nowpossible. However, the latest expansion of the density range (belowabout 0.912 g/cm.sup.3) has taken place only since the development ofthe single-site catalyst, also known in some versions as the Metallocenecatalyst.

U.S. Pat. No. 3,645,992 describes single-site catalysts capable ofproducing homogeneous polyethylenes. The homogeneity occurs because themolecules are much more similar to one another in terms of molecularweight and comonomer concentration. In other words, the high-molecularweight tail and the grease fraction are both largely eliminated with theDSC melting curve showing a single melting peak, as a result, asillustrated in FIG. 7. Cleanly flowing pellets, with no greasy feel,could be produced with densities as low as 0.880 g/cm.sup.3. Thesecatalysts are called single-site catalysts because all catalyst sitesencourage the growth of relatively similar polymer chains.

“Single-site catalysts” include metallocene or constrained-geometrycatalysts. Metallocene catalysts are organometallic co-ordinationcompounds obtained as a cyclopentadienyl (Cp) derivative of a transitionmetal or metal halide. The metal bonds to the Cp ring by electronsmoving in orbitals extending above and below the plane of the ring(pi-bond). Metallocene catalysts systems are extremely sensitive to thegeometry of the catalytic site at the transition metal (the“single-site”). Examples of single-site catalysts includeCp.sub.2TICl.sub.2, Cp.sub.2ZrCl.sub.2, Cp.sub.2HfCl.sub.2,(C.sub.5(CH.sub.3).sub.2).sub.3TiCl.sub.2, PH, Me(Ind).sub.2ZrCl.sub.2,[Me.sub.4CpSi(Me).sub.2N(t-Bu)]TiCH.sub.2[o-PhN(Me.sub.2)],Cp.sub.2FeB(C.sub.2F.sub.2).sub.4.

The ethylene copolymer made with single-site catalyst may be obtainedusing a variety of polymerization processes of the type described abovefor the manufacture of linear low density polyethylene, for example,processes that operate in solution, in the gas phase and as a slurryprocess; references to the use of single site catalysts inpolymerization processes is made in Modern Plastics, p. 15, May 1993,Plastics Focus Vol. 25, No. 12, Jun. 21, 1993 and in Exxon ChemicalExact Facts, Vol. 1, No. Feb. 1, 1993. Such polymers are obtained by thecopolymerization of ethylene with at least one C.sub.4-C.sub.10alpha-olefin hydrocarbon comonomer, examples of which include butene-1,hexene-1, and octene-1. The catalyst used is a so-called single-sitecatalyst, certain of which may also be referred to as metallocene orconstrained geometry catalysts.

In the present invention, if the linear polyethylene obtained with thesingle site catalyst is a low-density copolymer of ethylene and an atleast one C.sub.4-C.sub.10 alpha-olefin, then it has a density in therange of 0.905 to 0.935 g/cm.sup.3, preferably in the range 0.909 to0.930, and especially in the range 0.912 to 0.926 g/cm.sup.3. In otherembodiments, the density range can be defined by any two numbers fromabout 0.905, about 0.906, about 0.907, . . . , about 0.933, about 0.934,and about 0.935 g/cm.sup.3. In addition the low density copolymer has amelt-index in the range of 0.3 to 10.0 dg/min, preferably 0.3 to 2.0dg/min and especially in the range of 0.5 to 1.5 dg/min. In otherembodiments, the melt-index is in the range defined by any two numbersfrom about 0.3, about 0.4, about 0.5, . . . , about 9.8, about 9.9, andabout 10.0 dg/min.

If the linear polyethylene is used as a minor blend component, and is anultra-low-density copolymer of ethylene and an at least oneC.sub.4-C.sub.1. alpha-olefin, then it preferably has a density in therange of 0.8 to 0.909 g/cm.sup.3, moreover in the range of 0.859 to0.905 g/cm.sup.3, and especially in the range of 0.859 to 0.888g/cm.sup.3. In other embodiments, the density range can be defined byany two numbers from about 0.800, about 0.801, about 0.803, . . . ,about 0.907, about 0.908, and about 0.909 g/cm.sup.3. In addition, theultra-low-density polymer preferably has a melt-index of less than 5dg/min, particularly in the range of 0.4 to 1.1 dg/min and especially inthe range of 0.4 to 0.6 dg/min. In other embodiments, the melt-index isin the range defined by any two numbers from about 0.4, about 0.5, about0.6, . . . , about 0.9, about 1.0, and about 1.1 dg/min. In either case,the preferred copolymers include ethylene/butene-1, ethylene/hexene-1,ethylene/octene-1 and ethylene/hexene-1/butene-1 terpolymers.

Polypropylene is also polymerized using Zeigler-Natta, or single-sitecatalysts, or combinations of these catalysts.

Isotactic polypropylene homopolymer (“homoPP”) is a homogeneous polymernormally polymerized in a single stage reaction. It has a single cleanDSC melting peak in the region 160-165.degree. C. as illustrated in FIG.3 of the accompanying drawings.

Homogeneous polypropylene interpolymers (“HOPI”) also consist of asingle phase, and have a single clean DSC melting peak, which occurs ata lower temperature than that of the homopolymer. The energy of meltingof the homogeneous interpolymer is also somewhat lower than that of thehomopolymer. A typical DSC melting curve for a homogeneouspropylene-ethylene interpolymer is illustrated in FIG. 4 of theaccompanying drawings.

Heterogeneous polypropylene interpolymers (“HEPI”) are formed in a twostage reaction. In the first stage, a crystalline network of isotacticpolypropylene homopolymer or homogeneous polypropylene interpolymer isformed. In the second stage, a largely amorphous rubbery phase is formedwithin the crystalline network. A portion of the polymer formed in thesecond stage reaction is normally rich enough in comonomer, to be ableto crystallize to form a third phase. When the comonomer is ethylene,the third phase normally has a DSC melting peak in the 120-125.degree.C. region as illustrated in FIG. 5 of the accompanying drawings.

The blends useful in the present invention may be made by blending theconstituents prior to feeding to the hopper of a film extruder, or maybe made by blending the constituents at the time of extrusion just priorto remelting in the extruder, or alternatively the constituents may bemelt blended in the extruder.

The ethylene/alpha-olefin copolymer or blend of ethylene/alpha-olefincopolymers, for example, in pellet form, may be extruded into film formusing known techniques. One preferred method of manufacturing film isthe so-called blown film process. The film, after manufacture, is slitlongitudinally into appropriate widths. The width is selected on thebasis of the diameter of the tube to be formed on the vertical form,fill and seal apparatus. The preferred method of manufacture of amultilayer film is by using a blown film co-extrusion process, althoughother methods of manufacture of the film may be used.

The multilayer film of the invention is particularly useful in theformation of pouches, especially using a form, fill and seal apparatus.The pouches of the present invention may be used in the packaging offlowable materials, for example, liquids, as defined above. Inparticular, the pouches may be used in the packaging of milk.

In particular, the multilayer film provides increased stiffness,compared to the monolayer sealant film, increased clarity compared toHDPE film, increased sealability and toughness compared to PP film, andfurther improves efficiencies in the runnability and sealability ofmonolayer and prior art multilayer films as described herein.

Other Additives

In the present invention, sealant layers can have a combined weight of0-10 wt % of extrusion aid masterbatches including slip, antiblock andprocess aid. Interposed layers and core layers can have 0-2 wt % of slipmasterbatches.

It will be understood by those skilled in the art that additives such asantioxidants, UV stabilizers, anti-block agents, and slip additives, maybe added to the polymers from which the pouches of the present inventionare made. Optionally, the inner-sealant layer, the outer-sealant layer,the core and/or the first or the second interposed layer may furthercomprise one or several additives useful to make easier the processingof a film in a VFFS system, such as, for example, polymer processing aidconcentrate, and/or slip/antiblock concentrates. Any of such additiveswell known to person skilled in the art can be used. Advantageously, thefollowing additives are particularly preferred.

Slip Agent

The preferred range of the slip agent is from about 200 to 2000 ppm. Apreferred slip agent is erucamide or other fatty acid amide such asoleamide. The slip agent lowers the coefficient friction of the film andallows it to slide readily over various surfaces.

Anti-Blocking Agent

1000 to 5000 ppm of any film anti-blocking agent well known to skilledworkman maybe added to the film layers. Preferably from 1000 to 8000 ppmof an anti-blocking material such as diatomaceous earth, syntheticsilica or talc will be added to the inner and outer layers of the film.The anti-blocking material is particularly useful in reducing thecoefficient of friction between the film and the metallic surfaces overwhich the film is drawn during the VFFS process.

Processing Aid

50 to 1000 ppm of any processing aid well known to skilled workman,preferably and not limitatively containing a fluoro-elastomer basedpolymer may be added to outer and inner skin layers of the film.

Pouch-Making Processes

Pouch-making processes for VFFS are known in the art, for example, U.S.Patent Publication No. 2007/0254119, which is incorporated by referenceherein. The invention at hand also relates to a process for makingpouches filled with a flowable material, generally using a VFFSapparatus, wherein each pouch is made from a flat web of film by thefollowing steps:

(I) forming a tubular film therefrom with a longitudinal seal andsubsequently flattening said tubular film at a first position;

(II) transversely heat-sealing said tubular film at the flattenedposition;

(III) filling said tubular film with a predetermined quantity offlowable material above said first position;

(IV) flattening said tubular film above the predetermined quantity offlowable material at a second position; and

(V) transversely heat sealing said tubular film at said second position,wherein said pouches are made from a flat web of film made from amulti-layer film, comprising the following layers in order of an atleast one inner sealant-layer to an at least one outer sealant-layer:

(A) said at least one inner sealant-layer comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(B) a first at least one interposed layer adjacent to said at least oneinner sealant-layer, said first at least one interposed layercomprising:

(i) an at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(B)(i)(b);

wherein the centerline of said first at least one interposed layer iscloser to the centerline of said at least one inner sealant-layer thanto the centerline of said multi-layer film;

(C) at least one core layer, adjacent to said first at least oneinterposed layer, said at least one core layer comprising polyethylenethat is selected from the group consisting of:

at least one low-density ethylene-alpha olefin copolymer,

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process;

(D) a second at least one interposed layer adjacent to said at least onecore layer, said second at least one interposed layer comprising:

(i) an at least one polypropylene interpolymer and an at least onepolymeric compatibilizer, and at least one of:

(a) an at least one high-density polyethylene, or

(b) at least one ethylene-alpha-olefin copolymer; and

(ii) optionally, a second ethylene-alpha-olefin copolymer that is notthe same as said at least one ethylene-alpha-olefin copolymer in(D)(i)(b);

wherein the centerline of said second at least one interposed layer iscloser to the centerline of said at least one outer sealant-layer thanto the centerline of said multi-layer film; and

(E) said at least one outer sealant-layer, comprising polyethylene thatis selected from the group consisting of:

(i) an at least one low-density ethylene-alpha-olefin copolymer;

(ii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene homopolymer, wherein saidethylene homopolymer is made in a high-pressure polymerization process;and

(iii) a blend of said at least one low-density ethylene-alpha-olefincopolymer and an at least one ethylene copolymer, wherein said ethylenecopolymer is made in a high-pressure polymerization process; whereinsaid multi-layer film thickness is in the range of from about 35 micronsto about 66 microns; wherein a combined thickness of said first at leastone interposed layer and said second at least one interposed layer is inthe range of from about 10% to about 27% of the total thickness of saidmulti-layer film; and wherein a combined thickness of said innersealant-layer and said outer sealant-layer is in the range of from about10% to about 27% of the total thickness of said multi-layer film.

ABBREVIATIONS

-   -   BUR Blow-up ratio    -   EMA Ethylene methacrylate    -   EMAC Ethylene methacrylate copolymer    -   EPDM Ethylene propylene diamine rubber    -   EVA Ethylene-vinyl acetate    -   HDPE High-density polyethylene    -   HEPI heterogeneous polypropylene interpolymer    -   homoPP homopolymer polypropylene polymerized solely from        propylene monomer    -   HOPI homogeneous polypropylene interpolymer    -   HP-LDPE High-pressure, low-density polyethylene    -   LLDPE linear low-density polyethylene    -   MWD/SCBD Molecular weight/Short-chain branching distribution    -   PP Polypropylene    -   ULDPE Ultra low-density polyethylene    -   VA Vinyl acetate    -   PI polypropylene interpolymer polymerized from propylene and at        least one additional alpha-olefin monomer    -   VFFS Vertical Form, Fill, and Seal

EXPERIMENTAL

In the present set of experiments, generally, a multi-layer film is madeusing film extrusion processes that are well-known to the filmmanufacturing industry. The multi-layer film is extruded on a five-layerblown-film co-extrusion line. Films from the resin compositions of thisinvention can also be made using other film extrusion processes whichare well-known to the film manufacturing industry.

In one embodiment of the invention, which is a five-layer multi-layerfilm, the inner sealant-layer is designated as Layer A, the firstinterposed layer is designated as Layer B, the core layer is designatedas Layer C, the second interposed layer is designated as Layer D, andthe outer sealant-layer is designated as Layer E.

Three extruders (E.sub.A, E.sub.B, E.sub.C) feed an eight-inch diametercircular die used for preparing the film. Extruder E.sub.A feeds theouter sealant-layer (Layer E) and the inner sealant-layer (Layer A). The“sealant layer” extruder, E.sub.A, is a 2-inch diameter, single-screwextruder. Extruder E.sub.C feeds the first interposed layer (Layer B),and the second interposed layer (Layer D). The “interposed layer”extruder, E.sub.C, is also a 2-inch diameter, single-screw extruder.Extruder E.sub.B feeds the core layer (Layer C). The “core layer”extruder E.sub.B is a larger 4-inch diameter, single-screw extruder.

The co-extrusion line includes an oscillating nip, a corona-treater, anedge guide, and a back-to-back winder with slit-in-line that is capableof being surface-driven or centre-driven. The width of the tower nip andwinder also allow for blow-up ratios (“BUR”) up to about 4:1.Preferably, the BUR range from 1.5 to 2.8, which provides a stableprocess and good film quality. The melt processing temperatures of theresins in the extruders ranged from 150.degree. C. to 260.degree. C.Processing additives such as slip and antiblock are incorporated intothe resins as supplied or otherwise dry-blended in the form of additiveconcentrates, or melt-compounded into the resins throughmelt-compounding processes.

In one embodiment, the films are made at a BUR of 2:1. The films arewound as a flattened tube and slit to a narrower width.

For illustrative purposes, films with 12 different EXAMPLE resin recipesare manufactured on the co-extrusion line as described. The films aremade with a total thickness of 52 microns and the following layerthicknesses: A=4 microns, B=6 microns, C=32 microns, D=6 microns and E=4microns.

The films are run on the Prepac IS-7E filler to assess runnability, tomake pouches for evaluating in a pitcher, and to make pouches for apouch drop test. Pouches are made from the above-described multi-layerfilms (also see multi-layer film formulations, infra) using the VFFSprocess. It is normal to make pouches containing 1.3 liters of water, ata temperature of 4.0+/−0.5.degree. C., from a 24-cm wide film web;however, it is possible to make other pouch sizes if this is morerelevant to the specific end-use. The Prepac IS-7E vertical form, filland seal apparatus is normally equipped with an insulated transversesealing jaw (U.S. Pat. No. 5,538,590) and easy mount transverse sealingelement (PCT/CA98/00066 or equivalent). The web of film is formed into acontinuous tube with a lap seal, said tube having an inside diameter ofapproximately 9.8 cm. The operation of the vertical and transversesealing elements should be optimized for the particular film type andthickness used. It will be recognized that the sealing conditions (forexample, amperage, voltage, dwell time) depend on the gauge and meltingcharacteristics of the film. For example, a 50.mu.m film would requirelower amperage and/or voltage, as controlled by the rheostat on theapparatus, than would a 75.mu.m film. Typically such a change in filmthickness requires an adjustment of approximately 10% of the rheostatrange.

The drop test can be a constant height pouch drop test, or a Brucetonstair drop test, where the drop height is varied in a systematic way.Both procedures are adaptations of ASTM D5276: Drop Test of LoadedContainers by Free Fall. It should be verified that the pouches in thedifferent batches have very similar mean and standard deviation valuesfor weight, length, and headspace.

Constant Height Drop Test (Version of ASTM D5276 A2.2.1)

To compare the performance of one pouch film against another, at least200 well-made pouches should be manufactured from each film and droppedfrom a constant initial height in the range 10-15 feet. The pouchesshould be dropped before the water in them has had a chance to warm upappreciably. Each pouch is positioned with the longitudinal axis of thetube i.e. pouch, coincident with an imaginary horizontal line, thebottom surface of the pouch at the initial drop height, and the verticalseal facing upwards. In this orientation, the pouch is dropped onto astainless steel sheet, and then inspected visually and tactilely forleakers. Any pouch, from which water flows or weeps after the pouch hasbeen dropped, is termed a “leaker”. The number of leakers, expressed asa percentage of the total number of pouches dropped is the M(1.3)-testvalue for the particular film being tested, where 1.3 denotes the pouchsize in liters.

Bruceton Stair Drop Test (Version of ASTM D5276 A2.4.2)

The Bruceton Stair test is more discriminating, and requires only 40-50well-made pouches. The first pouch is positioned with the longitudinalaxis of the tube i.e. pouch, coincident with an imaginary horizontalline, the bottom surface of the pouch at a suitable initial drop height,say 8 feet, and the vertical seal facing upwards. In this orientation,the pouch is dropped onto a stainless steel sheet, and then inspectedvisually and tactilely for leakers.

If the first pouch survives the drop test intact without leaking water,then a new pouch is selected and dropped from a height of an additional0.5 feet, that is, 8.5 feet. On the other hand, if the first pouch is aleaker, then a new pouch is selected and dropped from a height, which islower by 0.5 feet, that is 7.5 feet. The testing continues, using a newpouch for every drop, until at least 5 passes and 5 failures haveoccurred in the height range where both passes and failures areoccurring. The 50% failure height is then calculated using thestatistical method of ASTM D5628.

Extrusion Aid Masterbatches

For the experimental examples described below, extrusion aids such asslip and anti-block are purchased as pelletized masterbatches fromIngenia Polymers (Houston, Tex.). The active ingredient is compoundedinto a polyethylene carrier resin, usually a 2-10 MI LLDPE resin.

TABLE A Masterbatch Active Ingredient Concentration Function IngeniaIP1065 Erucamide  5 wt % slip Ingenia IP1061A oleamide  5 wt % slipIngenia IP1142 fluoropolymer cpd  4 wt % Ingenia IT719 talc 30 wt %Ingenia IP1051 silica 25 wt %

A pellet blend of the major polyolefin resins, and these masterbatches,is fed to each extruder of the co-extrusion line. The various componentsof the pelletized mixture are fed into the main extruder hopper viasatellite blenders, the rates of which can be set to achieve the desiredmix ratio.

Example 1

Layers of the Multi-layer Film 1 are prepared with the resins andadditives shown in Table 1.

TABLE 1 Formulation for Multi-layer Film 1 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 72.5LLDPE Octene Single Site Homogeneous 0.917 1.00 MarflexD350 Chevron-25.0 LLDPE Hexane Single Site Honogeneous 0.933 0.90 Phillips IP1065Ingenia 1.8 LLDPE — — — 0.920 2-10MI carrier carrier IT 719 Ingenia 0.7LLDPE — — — 1.140 2-10MI carrier carrier First & Second Interposed-Layer(B & D); Extruder E_(C) Inspire PP D114 Dow 87.2 HEPI Minor componentSingle Site Heterogeneous 0.9 0.50 ethylene Reactor Blend CompatibilizedWestlake 8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0EMAC SP2207 Affinity PL 1880 Dow 3.0 ULDPE Octene Single SiteHomogeneous 0.902 1.0 IP1065 Ingenia 1.8 LLDPE — — — 0.920 2-10MIcarrier carrier Core-Layer (C); Extruder E_(B) Surpass FPs117C Nova 79.2LLDPE Octene Single Site Homogeneous 0.917 1.00 EquistarNA960 Lyondell-10.0 HP-LDPE None High Pressure Heterogeneous 0.919 1.0 Basell AffinityPL1880 Dow 9.0 ULDPE Octene Single Site Homogeneous 0.902 1.0 IP1065Ingenia 1.8 LLDPE — — — 0.920 2-10MI carrier carrier

Example 2

Layers of the Multi-layer Film 2 are prepared with the resins andadditives shown in Table 2.

TABLE 2 Formulation for Multi-layer Film 2 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 72.5LLDPE Octene Single Site Homogeneous 0.917 1.00 MarflexD350 Chevron-25.0 LLDPE Hexane Single Site Honogeneous 0.933 0.90 Phillips IP1065Ingenia 1.8 LLDPE — — — 0.920 2-10MI carrier carrier IT 719 Ingenia 0.7LLDPE — — — 1.140 2-10MI carrier carrier First & Second Interposed-Layer(B & D); Extruder E_(C) Inspire PP D114 Dow 87.2 HEPI Minor componentSingle Site Heterogeneous 0.9 0.50 ethylene Reactor Blend CompatibilizedWestlake 8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0EMAC SP2207 Engage8150 Dow 4.5 ULDPE Octene Single Site Homogeneous0.868 0.50 IP1065 Ingenia 1.8 LLDPE — — — 0.920 2-10MI carrier carrierCore-Layer (C); Extruder E_(B) Surpass FPs117C Nova 79.2 LLDPE OcteneSingle Site Homogeneous 0.917 1.00 EquistarNA960 Lyondell- 10.0 HP-LDPENone High Pressure Heterogeneous 0.919 1.0 Basell Engage8150 Dow 9.0ULDPE Octene Single Site Homogeneous 0.868 0.50 IP1065 Ingenia 1.8 LLDPE— — — 0.920 2-10MI carrier carrier

Example 3

Layers of the Multi-layer Film 3 are prepared with the resins andadditives shown in Table 3.

TABLE 3 Formulation for Multi-layer Film 3 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 72.5LLDPE Octene Single Site Homogeneous 0.917 1.00 MarflexD350 Chevron-25.0 LLDPE Hexane Single Site Honogeneous 0.933 0.90 Phillips IP1065Ingenia 1.8 LLDPE — — — 0.920 2-10MI carrier carrier IT 719 Ingenia 0.7LLDPE — — — 1.140 2-10MI carrier carrier First & Second Interposed-Layer(B & D); Extruder E_(C) Inspire PP D114 Dow 80.4 HEPI Minor componentSingle Site Heterogeneous 0.9 0.50 ethylene Reactor Blend CompatibilizedWestlake 8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0EMAC SP2207 Sclair RP020D Dow 10.0 ULDPE Octene Zeigler NattaHomogeneous 0.922 0.70 IP1065 Ingenia 1.6 LLDPE — — — 0.920 2-10MIcarrier carrier Core-Layer (C); Extruder E_(B) Sclair RP020D Nova 60.6LLDPE Octene Zeigler Natta Homogeneous 0.922 0.70 EquistarNA960Lyondell- 30.0 HP-LDPE None High Pressure Heterogeneous 0.919 1.0 BasellAffinity PL1880 Dow 9.0 ULDPE Octene Single Site Homogeneous 0.902 1.0IP1065 Ingenia 0.4 LLDPE — — — 0.920 2-10MI carrier carrier

Example 4

Layers of the Multi-layer Film 4 are prepared with the resins andadditives shown in Table 4.

TABLE 4 Formulation for Multi-layer Film 4 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Elite 5100G Dow 70.0 LLDPEOctene Single Site Heterogeneous 0.920 1.00 Reactor Blend MarflexD350Chevron- 25.0 LLDPE Hexane Single Site Honogeneous 0.933 0.90 PhillipsIP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier IP1052Ingenia 2.0 LLDPE — — — 1.000 2-10MI carrier carrier IP1142 Ingenia 1.0LLDPE — — — — — carrier First & Second Interposed-Layer (B & D);Extruder E_(C) Inspire PP D114 Dow 80.0 HEPI Minor component Single SiteHeterogeneous 0.9 0.50 ethylene Reactor Blend Compatibilized Westlake8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0 EMAC SP2207Elite 5100G Dow 10.0 LLDPE Octene Single Site Heterogeneous 0.920 0.85Reactor Blend IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carriercarrier Core-Layer (C); Extruder E_(B) Elite 5100G Dow 59.0 LLDPE OcteneSingle Site Heterogeneous 0.920 0.85 Blend PE 6621 Dow 30.0 HP-LDPE NoneHigh Pressure Heterogeneous 0.919 0.50 Engage8150 Dow 9.0 ULDPE OcteneSingle Site Homogeneous 0.868 0.50 IP1065 Ingenia 2.0 LLDPE — — — 0.9202-10MI carrier carrier

Example 5

Layers of the Multi-layer Film 5 are prepared with the resins andadditives shown in Table 5.

TABLE 5 Formulation for Multi-layer Film 5 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Elite 5100G Dow 94.5 LLDPEOctene Single Site Heterogeneous 0.920 0.85 Reactor Blend IP1065 Ingenia2.0 LLDPE — — — 0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE —— — 1.000 2-10MI carrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.9302-10MI carrier carrier First & Second Interposed-Layer (B & D); ExtruderE_(C) Inspire PP D114 Dow 80.0 HEPI Minor component Single SiteHeterogeneous 0.9 0.50 ethylene Reactor Blend Compatibilized Westlake8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0 EMAC SP2207Elite 5400G Dow 10.0 LLDPE Octene Single Site Heterogeneous 0.916 1.0Reactor Blend IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carriercarrier Core-Layer (C); Extruder E_(B) Elite 5100G Dow 68.0 LLDPE OcteneSingle Site Heterogeneous 0.920 0.85 Reactor Blend PE 6621 Dow 30.0HP-LDPE None High Pressure Heterogeneous 0.919 0.50 IP1065 Ingenia 2.0LLDPE — — — 0.920 2-10MI carrier carrier

Example 6

Layers of the Multi-layer Film 6 are prepared with the resins andadditives shown in Table 6.

TABLE 6 Formulation for Multi-layer Film 6 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Affinity PL1840G Dow 92.5LLDPE Octene Single Site Heterogeneous 0.909 1.0 IP1065 Ingenia 2.0LLDPE — — — 0.920 2-10MI carrier carrier IP1061A Ingenia 2.0 LLDPE — — —0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE — — — 1.000 2-10MIcarrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.930 2-10MI carriercarrier First & Second Interposed-Layer (B & D); Extruder E_(C) InspirePP D114 Dow 80.0 HEPI Minor component Single Site Heterogeneous 0.9 0.50ethylene Reactor Blend Compatibilized Westlake 8.0 EMAC MethacrylateHigh Pressure Heterogeneous 0.941 6.0 EMAC SP2207 Elite 5110G Dow 10.0LLDPE Octene Single Site Heterogeneous 0.9255 0.85 Reactor Blend IP1065Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier Core-Layer (C);Extruder E_(B) Surpass FPs117C Dow 68.0 LLDPE Octene Single SiteHomogeneous 0.917 1.0 PE 6621 Dow 30.0 HP-LDPE None High PressureHeterogeneous 0.919 0.50 IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MIcarrier carrier

Example 7

Layers of the Multi-layer Film 7 are prepared with the resins andadditives shown in Table 7.

TABLE 7 Formulation for Multi-layer Film 7 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Exceed 1015C Exxon- 94.5LLDPE Hexene Single Site Heterogeneous 0.915 1.0 Mobil Reactor BlendIP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier IP1051Ingenia 2.0 LLDPE — — — 1.000 2-10MI carrier carrier IP1142 Ingenia 1.5LLDPE — — — 0.930 2-10MI carrier carrier First & Second Interposed-Layer(B & D); Extruder E_(C) T14007G Sunoco 80.0 HEPI Minor componentZeigler-Natta Heterogeneous 0.9 0.70 ethylene Compatibilized Westlake8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.0 EMAC SP2207Elite 5110G Dow 10.0 LLDPE Octene Single Site Heterogeneous 0.9255 0.85Reactor Blend IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carriercarrier Core-Layer (C); Extruder E_(B) Surpass FPs117C Dow 68.0 LLDPEOctene Single Site Homogeneous 0.917 1.0 PE 1321 Dow 30.0 HP-LDPE NoneHigh Pressure Heterogeneous 0.922 0.22 IP1065 Ingenia 2.0 LLDPE — — —0.920 2-10MI carrier carrier

Example 8

Layers of the Multi-layer Film 8 are prepared with the resins andadditives shown in Table 8.

TABLE 8 Formulation for Multi-layer Film 8 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 85.5LLDPE Octene Single Site Homogeneous 0.917 1.0 Engage8150 Dow 9.0 ULDPEOctene Single Site Homogeneous 0.868 0.50 IP1065 Ingenia 2.0 LLDPE — — —0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE — — — 1.000 2-10MIcarrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.930 2-10MI carriercarrier First & Second Interposed-Layer (B & D); Extruder E_(C) InspirePP D114 Dow 65.0 HEPI Minor component Single Site Heterogeneous 0.9 0.70ethylene Reactor Blend Compatibilized Westlake 8.0 EMAC MethacrylateHigh Pressure Heterogeneous 0.941 6.0 EMAC SP2207 Sclair 19C Nova 25.0HDPE None Zeigler-Natta Heterogeneous 0.9258 0.95 IP1065 Ingenia 2.0LLDPE — — — 0.920 2-10MI carrier carrier Core-Layer (C); Extruder E_(B)Surpass FPs117C Dow 68.0 LLDPE Octene Single Site Homogeneous 0.917 1.0PE 6621 Dow 30.0 HP-LDPE None High Pressure Heterogeneous 0.919 0.5IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier

Example 9

Layers of the Multi-layer Film 9 are prepared with the resins andadditives shown in Table 9.

TABLE 9 Formulation for Multi-layer Film 9 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 85.5LLDPE Octene Single Site Homogeneous 0.917 1.0 Engage8150 Dow 9.0 ULDPEOctene Single Site Homogeneous 0.868 0.50 IP1065 Ingenia 2.0 LLDPE — — —0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE — — — 1.000 2-10MIcarrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.930 2-10MI carriercarrier First & Second Interposed-Layer (B & D); Extruder E_(C) InspirePP D114 Dow 45.0 HEPI Minor component Single Site Heterogeneous 0.9 0.50ethylene Reactor Blend Compatibilized Westlake 8.0 EMAC MethacrylateHigh Pressure Heterogeneous 0.941 6.0 EMAC SP2207 Elite 5960G Nova 45.0HDPE None Single Site Heterogeneous 0.962 0.85 Reactor Blend IP1065Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier Core-Layer (C);Extruder E_(B) Surpass FPs117C Dow 68.0 LLDPE Octene Single SiteHomogeneous 0.917 1.0 PE 6621 Dow 30.0 HP-LDPE None High PressureHeterogeneous 0.919 0.22 IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MIcarrier carrier

Example 10

Layers of the Multi-layer Film 10 are prepared with the resins andadditives shown in Table 10.

TABLE 10 Formulation for Multi-layer Film 10 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 94.5LLDPE Octene Single Site Homogeneous 0.916 0.65 IP1065 Ingenia 2.0 LLDPE— — — 0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE — — — 1.0002-10MI carrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.930 2-10MIcarrier carrier First & Second Interposed-Layer (B & D); Extruder E_(C)Inspire PP D114 Dow 40.0 HEPI Minor component Single Site Heterogeneous0.9 0.75 ethylene Reactor Blend Compatibilized Westlake 8.0 EMACMethacrylate High Pressure Heterogeneous 0.941 6.0 EMAC SP2207 Elite5960G Dow 50.0 HDPE None Single Site Heterogeneous 0.962 0.85 ReactorBlend IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrierCore-Layer (C); Extruder E_(B) Surpass FPs117C Dow 68.0 LLDPE OcteneSingle Site Homogeneous 0.916 0.65 PE 1231 Dow 30.0 HP-LDPE None HighPressure Heterogeneous 0.922 0.22 IP1065 Ingenia 2.0 LLDPE — — — 0.9202-10MI carrier carrier

Example 11

Layers of the Multi-layer Film 11 are prepared with the resins andadditives shown in Table 11.

TABLE 11 Formulation for Multi-layer Film 11 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Surpass FPs117C Nova 85.5LLDPE Octene Single Site Homogeneous 0.917 1.0 Engage8150 Dow 9.0 ULDPEOctene Single Site Homogeneous 0.868 0.50 IP1065 Ingenia 2.0 LLDPE — — —0.920 2-10MI carrier carrier IP1051 Ingenia 2.0 LLDPE — — — 1.000 2-10MIcarrier carrier IP1142 Ingenia 1.5 LLDPE — — — 0.930 2-10MI carriercarrier First & Second Interposed-Layer (B & D); Extruder E_(C) 4170Total 75.0 HEPI Minor component Zeigler-Natta Heterogeneous 0.905 0.75Petrochemicals ethylene Compatibilized Westlake 8.0 EMAC MethacrylateHigh Pressure Heterogeneous 0.941 6.0 EMAC SP2207 Dowlex 2045G Dow 15.0LLDPE None Zeigler-Natta Heterogeneous 0.920 1.00 IP1065 Ingenia 2.0LLDPE — — — 0.920 2-10MI carrier carrier Core-Layer (C); Extruder E_(B)Surpass FPs117C Dow 73.0 LLDPE Octene Single Site Homogeneous 0.917 1.0PE 1231 Dow 25.0 HP-LDPE None High Pressure Heterogeneous 0.922 0.22IP1065 Ingenia 2.0 LLDPE — — — 0.920 2-10MI carrier carrier

Example 12

Layers of the Multi-layer Film 10 are prepared with the resins andadditives shown in Table 12.

TABLE 12 Formulation for Multi-layer Film 12 Resin Resin Catalyst ResinGrade/Trade Weight % Polymer in Resin MWC/ Destiny; Melt-index NameSupplier of Layer Type Comonomer Manufacture SCBD g/cm³ deci g/min Inner& Outer Sealant-Layer (A & E); Extruder E_(A) Enable20-10CE Exxon- 98.0LLDPE Hexene Single Site Heterogeneous 0.92 1.0 Moblil Reactor BlendIP1065 Ingenia 1.0 LLDPE — — — 0.920 2-10MI carrier carrier IP1051Ingenia 2.0 LLDPE — — — 1.000 2-10MI carrier carrier IP1142 Ingenia 1.0LLDPE — — — 0.930 2-10MI carrier carrier First & Second Interposed-Layer(B & D); Extruder E_(C) T14005F Sunoco 80.1 HEPI Minor componentZeigler-Natta Heterogeneous 0.9 0.50 ethylene Compatibilized Westlake8.0 EMAC Methacrylate High Pressure Heterogeneous 0.941 6.00 EMAC SP2207Enable20-10CE Exxon- 10 LLDPE Hexene Single Site Heterogeneous 0.92 1.0Moblil Reactor Blend IP1065 Ingenia 1.9 LLDPE — — — 0.920 2-10MI carriercarrier Core-Layer (C); Extruder E_(B) Enable20-10CE Exxon- 85 LLDPEHexene Single Site Homogeneous 0.92 1.0 Moblil Reactor Blend Affinity PL1880 Dow 15 ULDPE Octene Single Site Homogeneous 0.920 1.0

What is claimed:
 1. A process for making pouches filled with a flowablematerial, using a vertical form, fill and seal apparatus, wherein eachpouch is made from a flat web of film by the following steps: (I)forming a tubular film therefrom with a longitudinal seal andsubsequently flattening said tubular film at a first position; (II)transversely heat-sealing said tubular film at the flattened position;(III) filling said tubular film with a predetermined quantity offlowable material above said first position; (IV) flattening saidtubular film above the predetermined quantity of flowable material at asecond position; and (V) transversely heat sealing said tubular film atsaid second position, wherein said pouches are made from a flat web offilm made from a multi-layer film, consisting of the following layers inorder, an at least one inner sealant-layer, a first at least oneinterposed layer adjacent to said one inner sealant layer, an at leastone core layer adjacent to said interposed layer, an at least a secondinterposed layer adjacent to said core layer and at an at least oneouter sealant-layer adjacent to said second interposed layer: (A) saidat least one inner sealant-layer and said outer sealant layer eachconsisting of: (i) from about 85 to about 98 parts by weight of alow-density copolymer of ethylene and an at least one C₄-C₁₀,alpha-olefin manufactured in a polymerization process using asingle-site polymerization catalyst, with a density in the range of fromabout 0.909 to about 0.935 g/cm³ and a melt-index in the range of fromabout 0.5 to about 1.5, and (ii) from about 2 to about 15 parts byweight of an additional at least one low-density copolymer of ethyleneand an at least one C₄-C₁₀ alpha-olefin, which is an ultra-low densitycopolymer of ethylene and at least one C₄-C₁₀ alpha-olefin manufacturedin a polymerization process using a single-site polymerization catalyst,with a density in the range of from about 0.859 to about 0.888 g/cm³ anda melt-index in the range of from about 0.4 to about 0.6 dg/min; (B)said first at least one interposed layer adjacent to said at least oneinner sealant layer and said second interposed layer each consisting of:(i) at least one polypropylene interpolymer in the range of from about40 to about 95 parts by weight of said first at least one interposedlayer, wherein said polypropylene interpolymer has a melt-index in therange of from about 0.45 to about 0.75 dg/min, at least one high-densitypolyethylene is in the range of from about 0 to about 50 parts by weightof said first at least one interposed layer, wherein said at least onehigh-density polyethylene is manufactured in a polymerization processusing a single-site polymerization catalyst or a Ziegler-Natta catalyst,wherein said at least one high-density polyethylene has a densitygreater than about 0.935 g/cm³ but less than about 0.970 g/cm³ and amelt-index in the range of from about 0.75 to about 1.05 dg/min, and atleast one polymer compatibilizer in the range of from about 2 to about10 parts by weight of said first at least one interposed layer; and (ii)at least one ethylene-alpha olefin copolymer in the range from 0 toabout 15 parts by weight of said first at least one interposed layer,wherein at least one C₄-C₁₀ alpha-olefin is an ultra-low densitycopolymer of ethylene and at least one C₄-C₁₀ alpha-olefin manufacturedin a polymerization process using a single-site polymerization catalyst,with a density in the range of from about 0.859 to about 0.905 g/cm³ anda melt-index in the range of from about 0.4 to about 1.1 dg/min, and(iii) at least one additional ethylene-alpha-olefin copolymer in therange of from about 0 parts to 15 parts by weight, manufactured in apolymerization process using either a single-site or Zeigler-Nattapolymerization catalyst, wherein said copolymer has a density in therange of from about 0.909 to about 0.935 g/cm³ and a melt-index in therange of from about 0.5 to about 1.5 dg/min; and (C) at least one corelayer, adjacent to said first at least one interposed layer and saidsecond interposed layer, said core layer consisting of: i) at least onelow density ethylene-alpha olefin copolymer in the range from 35 toabout 85 parts by weight of said at least one core layer manufactured ina polymerization process using either a single-site or ZeiglerNattapolymerization catalyst, wherein said copolymer has a density in therange of from about 0.909 to about 0.935 g/cm³ and a melt-index in therange of from about 0.5 to about 1.5 dg/min; (ii) an at least onelow-density copolymer of ethylene and an at least one C₄-C₁₀alpha-olefin in the range of about 0-15 parts by weight of said at leastone core layer, which is an ultra-low density copolymer of ethylene andat least one C₄-C₁₀ alpha-olefin manufactured in a polymerizationprocess using a single-site polymerization catalyst, with a density inthe range of from about 0.859 to about 0.905 g/cm³ and a melt-index inthe range of from about 0.4 to about 1.1 dg/min; and (iii) at least onelow-density ethylene homopolymer or copolymer, made in a high pressurepolymerization process, in the range of from about 10 parts to 50 partsby weight of said at least one core layer, wherein the ethylenehomopolymer has a density in the range of from about 0.918 to about0.923 g/cm³ and a melt-index in the range of from about 0.1 to 1.1dg/min, and the ethylene copolymer has a density in the range of fromabout 0.930 to about 0.960 g/cm³ and a melt-index in the range of fromabout 0.1 to about 10 dg/min. and wherein the combined thickness of saidfirst and second interposed layers is in the range of from about 10% toabout 27% of the total thickness of said multilayer film and wherein thecombined thickness of said inner and outer sealant-layers are in a rangeof from about 10% to about 27% of the total thickness of saidmulti-layer film and wherein the core layer thickness ranges from about46% to about 80% of the total thickness of the multi-layer film, andwherein said multilayer film thickness is in the range of from about 38microns to about 63 microns.
 2. The process of claim 1 wherein thepolypropylene interpolymer of the multilayer film consists of aninterposed layer of a heterogeneous or homogeneous copolymer ofpolypropylene or blend of copolymer polypropylenes with homopolymerpolypropylenes.
 3. The process of claim 2 wherein said polypropyleneinterpolymer is a polypropylene or blend of polypropylenes with izodimpact strength of greater than 9 ft-lb_(f) per inch of notch as perAmerican Society for Testing and Materials (ASTM) D
 256. 4. The processof claim 1 wherein said multi-layer film has a thickness is in the rangeof from about 44 microns to about 60 microns.
 5. The process of claim 1wherein said multi-layer film thickness is in the range of from about 47microns to about 59 microns.